JPH05335Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasticizing device for an injection molding machine that plasticizes and injects resin with a screw inserted into a heating cylinder.

[Prior Art] This type of plasticizing device for an injection molding machine plasticizes the resin and stores it on the tip side of the screw in the heating cylinder by rotating the screw, and at this time, the resin on the tip side is The screw moves toward the proximal end (rearward) in the axial direction due to the pressure, and by detecting the retracted position of the screw, the amount of resin stored on the distal end side of the screw is measured.
When a limit switch or the like detects that the retracted position of the screw has reached the preset metering completion position, the rotation drive means of the screw is turned off and the screw stops naturally due to resistance such as the viscosity of the resin. This causes the screw to stop moving in the axial direction. Also, when injecting the resin stored on the tip side of the screw,
The screw is moved axially toward the tip from the axial stop position to the injection completion position, thereby injecting the resin at the tip from the nozzle into the mold.

Therefore, in the plasticizing device of the injection molding machine, by reducing the variation in the axial stop position and injection completion position of the screw,
Variations in the amount of resin injected into the mold are reduced, making it possible to obtain precision molded products with small variations.

However, there is a problem in that the stopping position of the screw in the axial direction tends to change depending on the rotational speed of the screw, the viscosity of the resin, etc.

For this reason, for example, the rotational speed of the screw may be changed to a low speed near a limit switch, etc., thereby suppressing variations in the stop position in the axial direction of the screw, or after the metering completion position is detected by a limit switch, etc., the screw rotation speed may be changed to a low speed. Techniques have been developed to forcibly stop the movement in the direction using a mechanical stopper. However, in the case of the latter technology in which the axial movement of the screw is stopped using a mechanical stopper, even when the axial movement of the screw is stopped, the screw may continue to rotate or stop. is possible. Therefore, when stopping with a mechanical stopper, even if the variation in the stop position in the axial direction of the screw is reduced, the pressure of the resin stored at the tip side of the screw will vary in height, and as a result, However, this method has the disadvantage of causing variations in the amount of the resin, and is not considered to be a good means for reducing variations in molded products.

Therefore, in the plasticizing device of a conventional injection molding machine, the rotational speed of the screw is usually switched to a low speed near a limit switch, etc., thereby suppressing variations in the axial stop position of the screw, and molded products. The aim is to reduce the variation in

[Problem to be solved by the invention] However, in the plasticizing device of the above injection molding machine, the pressure of the resin on the tip side of the screw increases during plasticization, but this pressure continues even after the rotation of the screw has stopped. Resin may remain and resin may leak from the nozzle. In such a case, the screw is retracted toward the proximal end in the axial direction without rotation to reduce the pressure on the resin. Therefore, if the stop position of the screw varies due to non-rotational retreat, the injection start position will vary, resulting in variations in the molded product.

Therefore, the above-mentioned conventional technique of reducing the rotational speed of the screw before detection by a limit switch or the like is not an effective means for reducing the variation in molded products when the screw is retracted without rotation. No.

The present invention was devised in view of the above circumstances, and is a plasticization method for an injection molding machine that can reduce the variation in the axial stop position of the screw during non-rotational retraction, thereby reducing the variation in molded products. The purpose is to provide equipment.

[Means for Solving the Problems] In order to achieve the above object, the present invention reduces the pressure of the resin on the tip side of the screw inside the heating cylinder by retracting the screw inserted into the heating cylinder without rotation. In the plasticizing device for an injection molding machine having a non-rotational retraction means, the non-rotation retraction means is provided with a mechanical stopper for regulating the amount of non-rotation retraction of the screw.

[Function] In the present invention, since the amount of non-rotation retraction of the screw is regulated by the mechanical stopper, the variation in the non-rotation retraction position becomes almost zero. Therefore, the variation in the injection start position of the screw becomes almost zero, the variation in the amount of resin injected into the mold becomes extremely small, and the variation in the molded product also becomes extremely small.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, 1 is a heating cylinder, and a nozzle 2 is provided at the tip of this heating cylinder 1.
A flange member 3 is fitted to the outer periphery of the proximal end of the flange member 3.
is fixed. The flange member 3 is provided with a hopper 5 for supplying resin into the heating cylinder 1 through a hole 4 passing through the flange member 3 and the wall of the heating cylinder 1. Further, a screw 6 is inserted into the heating cylinder 1, and this screw 6 is
By rotating, the resin supplied from the hopper 5 is plasticized and sent to the tip side, and by moving toward the tip side in the axial direction, the resin at the tip side of the screw is transferred to the metal via the nozzle 2. It is designed to be injected into the mold. The screw 6 is connected at its base end to a hydraulic motor 7 to be driven to rotate, and is also connected to a piston rod 8a of a hydraulic cylinder 8 via the hydraulic motor 7 to be driven to move in the axial direction. It is becoming more and more common.

Further, the hydraulic motor 7 is provided with a mechanical stopper mechanism 9 for regulating the amount of movement of the screw 3 in the backward direction. This mechanical stopper mechanism 9 includes a stopper 10 that protrudes outward from the outer periphery of the hydraulic motor 7 and has a through hole 10a that is penetrated in parallel to the axial direction of the screw 6. The male threaded portion 11a is inserted,
A threaded rod 11 whose base end is connected to the flange member 3
and a male threaded portion 11 on the distal side of the stopper 10.
A and a nut 12 screwed together. The mechanical stopper mechanism 9 and the hydraulic cylinder 8 constitute non-rotational retraction means for the screw.

Further, a linear encoder (not shown) is connected to the hydraulic motor 7 and the flange member 3, so that the axial position of the screw 6 with respect to the heating cylinder 1 can be detected.

In the plasticizing device of the injection molding machine configured as described above, when hydraulic oil is supplied to the hydraulic motor 7 to rotate the screw 6, the resin supplied from the hopper 5 is plasticized and the screw 6 is rotated. Sent to the tip side. Then, due to the pressure of the resin stored on the tip side of the screw 6, the screw 6
moves proximally. However, at this time, since the tip of the nozzle 2 is in contact with the mold that has injected the resin first and is being cooled, the resin will not leak from the nozzle 2. Then, by detecting the amount of movement of the screw 6 toward the proximal end with a linear encoder,
The amount of resin stored on the tip side of the screw 6 is measured, and when the amount of resin reaches a preset value, the supply of hydraulic oil to the hydraulic motor 7 is stopped, and the rotation of the screw 6 is stopped. Stops naturally due to viscosity resistance. Next, when hydraulic oil is supplied to the rod side of the hydraulic cylinder 8 (solid line arrow A side in the figure), the screw 6 is moved backward without rotation, and then stopped by the stopper 10 coming into contact with the nut 12. Even after the screw 6 stops, hydraulic oil is continued to be supplied to the rod side of the hydraulic cylinder 8, thereby maintaining the position of the screw 6 at a position regulated by a stopper 10 and a nut 12.

In addition, once the resin injected into the mold has been completely cooled and the molded product is taken out, the direction of the hydraulic oil supplied to the hydraulic cylinder 8 is switched from the rod side to the head side (dotted line arrow B side in the figure). Then, the piston rod 8a is extended and the screw 6 is moved toward the tip side in the axial direction. Then, the resin stored on the tip side of the screw 6 is injected into the mold through the nozzle 2. After the screw 6 has moved to a preset injection completion position, the process moves to a pressure holding step, and the pressure of the hydraulic oil supplied to the head side of the hydraulic cylinder 8 is controlled.

After the pressure holding process is completed, the supply of hydraulic oil to the hydraulic rod 8 is stopped, and the piston rod 8a becomes freely movable in the axial direction. In this state, hydraulic oil is supplied to the hydraulic motor 7 again to rotate the screw 6,
Plasticize the resin.

By repeating the above operations, many molded products are molded.

In the plasticizing device of the injection molding machine configured as described above, the mechanical stopper mechanism 9
The stop position of the screw 6 in its non-rotational backward movement is regulated, and the axial position of the screw 6 is adjusted by the thrust of the hydraulic cylinder 8 to a mechanical stopper mechanism 9.
Since the injection starting position is held at a position regulated by Therefore, it is possible to extremely reduce variations in the amount of resin injected into the mold, making it possible to mold precise molded products with small variations.

In the above embodiment, the linear encoder is connected to the hydraulic motor 7 and the flange member 3, but by connecting it to the hydraulic motor 7 and the hydraulic cylinder 8, the axial direction of the screw 6 with respect to the heating cylinder 1 can be adjusted. It goes without saying that it may be configured to detect the position.

Further, although the linear encoder is used to detect the axial position of the screw, it goes without saying that a limit switch or other appropriate electrical position detecting means may be used instead of the linear encoder.

Further, instead of the hydraulic motor 7, an electric motor or other rotational drive means may be provided to rotationally drive the screw 6, and instead of the hydraulic cylinder 8, an electric motor or other rotational drive means may be used.
The screw 6 may be moved in the axial direction by a linear drive device including a mechanism for converting the rotational drive force obtained by the rotation drive means into a linear drive force.

[Effect of the invention] As explained above, according to the invention, the screw inserted into the heating cylinder is retracted without rotation, and the pressure of the resin on the tip side of the screw inside the heating cylinder is reduced. In the plasticizing device for an injection molding machine, the non-rotation retraction means is provided with a mechanical stopper for regulating the amount of non-rotation retraction of the screw, so that variations in the non-rotation retraction position of the screw can be reduced to almost zero. can do. Therefore,
Since the variation in the injection start position of the screw can be reduced to almost zero, the variation in the amount of resin injected into the mold can be extremely reduced, making it possible to mold precision molded products with small variation. can.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a plasticizing device of an injection molding machine showing an embodiment of the present invention. 1... Heating cylinder, 6... Screw, 9... Mechanical stopper mechanism.

Claims (1)

[Scope of utility model registration request] In the plasticizing device for an injection molding machine, the plasticizing device includes a non-rotation retraction means for retracting the screw inserted into the heating cylinder without rotation to reduce the pressure of the resin accumulated on the tip side of the screw in the heating cylinder. A plasticizing device for an injection molding machine, wherein the non-rotation retraction means is provided with a mechanical stopper for regulating the amount of non-rotation retraction of the screw.